Hypothalamic neurons, among which include AgRP and POMC neurons in the arcuate nucleus, detect changes in nutritional status and relay signals to downstream targets to regulate food intake and energy expenditure. Dysfunction of these neurons is believed to cause obesity and anorexia nervosa. The mechanism, however, is still poorly understood. Attention has been primarily focused on the regulation of these neurons by humoral factors, like insulin, leptin, and ghrelin. The synaptic regulation of these neurons, on the other hand, which is likely to be important, has been largely overlooked. Our preliminary studies have revealed a critical role for NMDA receptors and dendritic spines on AgRP neurons. Left unknown, however, are the mechanisms behind this regulation. Thus, the goal of this project is to determine the role of NMDA receptors and the synapses that form on individual dendritic spines of AgRP neurons, and to identify the specific signaling mechanisms that operate within the spines. However, technical challenges to observing and stimulating localized activity at single synapses have prevented the achievement of this goal. Advanced approaches like 2-photon laser scanning microscopy (2PLSM) and 2-photon uncaging of glutamate (2PLU) need to be employed. These powerful technologies occupy a unique niche in understating synaptic functions. With mentoring by Dr. Brad Lowell, an expert in mouse genetics and the hypothalamus, and co- mentoring by Dr. Bernardo Sabatini, a leading expert in synaptic plasticity and dendritic spines, a combination of approaches will be used to assess synaptic regulation of AgRP neurons. Specifically, 2PLU/2PLSM, in combination with electrophysiology and calcium imaging will be used to determine how the synaptic plasticity of excitatory neurotransmission to AgRP neurons is regulated by feeding-related signals. These studies should provide mechanistic insight into the regulation of AgRP neuron activity, and consequently, a better understanding of how feeding behavior is controlled. The applicant is now an Instructor of Medicine in the Division of Endocrinology, Dept. of Medicine, at Beth Israel Deaconess Medical Center and Harvard Medical School. The proposed studies will be performed at BIDMC as the primary location and Dept. of Neurobiology of Harvard Medical School as the second location. With the support of the Mentored Research Scientist Development Award, the applicant will be trained both technically and intellectually. The training to be supported by this award will greatly facilitate the applicant becoming a successful independent investigator in employing unique skill sets to address key questions in the neuroscience of feeding.